This invention relates to a shaft seal, and more particularly to a molded shaft seal having a case and a resilient sealing element which are secured together in a molding process.
Various shaft seals are known in the prior art, some of which incorporate a resilient sealing element for engaging the shaft. The resilient sealing element may be formed of a relatively hard material such as PTFE to improve durability. Seals of this type are used in demanding applications such as in the compressor of an automobile air conditioning system.
In some prior art constructions of seals incorporating a PTFE sealing element, adhesives or the like are used to adhere the PTFE sealing element to a case or housing. Some examples are shown in Hatch U.S. Pat. No. 5,052,696 and U.S. Pat. Nos. 5,149,106 and 5,056,799 to Takenaka et al.
It is also known in the prior art to utilize an elastomeric material, such as rubber, to secure the PTFE sealing element to the case or housing, such as is shown in Wada et al U.S. Pat. No. 5,183,271. In the Wada et al '271 patent, the PTFE element is pre-assembled to the case, and this assembly is preformed to an L-shape and is then held in a mold cavity while the elastomeric material is introduced into the mold cavity in a liquid state, resulting in a final assembly in which the PTFE element and the axial portion of the case are encased by the elastomeric material.
It is an object of the present invention to provide an improved molded seal construction in which a PTFE sealing element and the case are secured or held together using an elastomeric material, such as rubber. It is a further object of the invention to simplify the structure of a seal incorporating a PTFE sealing element, and to simplify the manner in which such a seal construction is attained. A still further object of the invention is to provide a seal having a PTFE sealing element in which leak paths through the interior of the seal are eliminated. Yet another object of the invention is to provide an improved arrangement for preventing rotation between the case and the PTFE sealing element.
In accordance with one aspect of the invention, a shaft seal includes a case which defines an axial portion and a radial portion. A resilient sealing member, preferably formed of a material such as PTFE, includes an outer portion positioned inwardly of the case axial portion and against the case radial portion, and an inner portion extending at an angle relative to the outer portion inwardly of the radial portion of the case. The resilient sealing member terminates in an inner edge engageable with the shaft and deflectable upon contact of the sealing member with the shaft. An elastomeric material, such as rubber, surrounds the axial portion of the case and engages at least a portion of the case radial portion and the outer portion of the sealing member, for holding the case and the resilient sealing member together to form a seal construction. The outer portion of the resilient sealing member includes notches in which the elastomeric material is received, so as to prevent rotation between the sealing member and the case. The notches are formed in an outer peripheral edge of the resilient sealing member, located adjacent the case axial portion. The elastomeric material is preferably formed so as to define an auxiliary seal engageable with the shaft, adjacent the inner portion of the resilient sealing member. In addition, the elastomeric material is preferably further formed so as to define an excluder lip seal engageable with the shaft and extending from the inner edge of the case radial portion. The inner portion of the resilient sealing member extends in a first direction relative to the case radial portion, and the excluder lip seal extends from the case radial portion in a second direction opposite the first direction. With this construction, the inner portion of the resilient sealing member is located between the excluder lip seal and the auxiliary seal, both of which are defined by the elastomeric material. The elastomeric material overlies the inner edge of the case radial portion between the excluder lip seal and the inner portion of the resilient sealing member, and defines an outer ring which encases the case axial portion. The elastomeric material further includes connecting structure extending between the outer ring and the excluder lip seal. The connecting structure at least partially overlies the case radial portion, and may be in the form of a series of spaced, radially extending connectors which extend between the excluder lip seal and the outer ring.
In accordance with another aspect of the invention, a method of constructing a shaft seal includes the steps of providing a case and a resilient sealing member, both of which are constructed as summarized above. The resilient sealing member is positioned against the radial portion of the case, such that the inner portion of the resilient sealing member extends inwardly of the case radial portion. The case axial portion and at least part of the sealing member outer portion and the case radial portion are encased with an elastomeric material to hold the case and resilient sealing member together to form a unitary seal construction. Thereafter, the inner portion of the resilient sealing member is deflected relative to the sealing member outer portion, to facilitate engagement of the sealing member with the shaft. The resilient sealing member is initially in the form of a disc-like member having an aperture therethrough. The step of positioning the resilient sealing member against the case radial portion is carried out by clamping the case radial portion and the disc-like resilient sealing member together between a pair of mold sections, at least one of which defines a mold cavity about the case axial portion and the outer portion of the resilient sealing member. The encasing step is carried out while the case and the resilient sealing member are clamped between the pair of mold sections, by introducing the elastomeric material in a liquified state into the mold cavity and thereafter solidifying the elastomeric material to hold the case and the sealing member together to form a unitary seal construction. The step of deflecting the inner portion of the resilient sealing member is carried out by removing the unitary seal construction from the mold sections after the elastomeric material is solidified, and thereafter holding the seal construction while engaging the inner portion of the resilient sealing member with a mandrel having an angled end. The method further includes the step of forming an excluder lip seal with the elastomeric material, inwardly of the inner edge of the case radial portion. The elastomeric material is formed to define an outer ring which encases the case axial portion, and the step of forming the excluder lip seal is carried out by forming the elastomeric material such that the elastomeric material at least partially overlies the case radial portion between the outer ring and the excluder lip seal. The excluder lip seal is formed so as to extend inwardly of the inner edge of the case radial portion, so that the elastomeric material adjacent the excluder lip seal overlies the inner edge of the case radial portion.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.